Over the last two years, Sars-CoV-2, the virus that causes Covid-19, has killed more than six million people worldwide and tens of millions of survivors have long-term health issues. While there have been many infectious disease pandemics in the past, including the black death, the great plague, Aids, Spanish flu and swine flu, and new pandemics were predicted, the world was still taken by surprise. Ireland did a comparatively good job in dealing with the Covid-19 pandemic. However, Ireland, like many countries, was ill-prepared to deal with a highly transmissible virus that infected so many people and had our healthcare system on its knees.
So, the big questions now are: how much have we learned and how will we respond to the next pandemic? We know that future infectious disease pandemics are inevitable, but we cannot know the precise cause of these pandemics, nor when or how seriously we’ll be affected. In recent weeks, we have learned that adenovirus is perhaps causing hepatitis in children across the globe and, of course, monkey pox has recently infected humans in Ireland, Europe and the US.
Natural hosts
There have been sporadic reports of human infections with monkey pox but, right now, the case numbers are escalating significantly and we do not know why. The monkey pox virus belongs to the same family as the smallpox virus, which killed over 300 million people across the world (more than one in five of all those infected), until an effective vaccine completely eliminated the virus over 40 years ago. The natural hosts of monkey pox are probably rodents rather than monkeys, although the virus can transmit from a variety of species. Transmission in humans is by direct contact with skin lesions, respiratory secretions or other bodily fluids of an infected person or animal. In comparison with Sars-CoV-2, the risk of airborne transmission of monkey pox is low. Infected individuals develop a fever, rash and skin lesions and, while most people recover after two to four weeks, the infection can be fatal in 1-10 per cent of cases. The vaccine that successfully eliminated smallpox is also effective against monkey pox. However, this vaccine was discontinued in the 1970s so, right now, only older people will have any level of immunity against monkey pox. The good news is that production of the smallpox vaccine could readily be resumed if required, although the early signs are that monkey pox will not develop into another pandemic.
So, what else might cause the next pandemic? Bacteria resistant to antibiotics, including methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant tuberculosis are current and future threats. Meanwhile, the unpredictability of zoonotic diseases, where microbes spread from animals to humans, continues to pose the biggest future threat to human health. When viruses cross a species barrier, they can be less or more pathogenic (disease-causing) in their new host. Animal viruses that cross from animals to humans and then readily transmit from human to human, and cause severe disease in a population that lacks immunity from previous infection, pose the greatest threat. This was the case with Sars-CoV-2, as well as with avian and swine flu.
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Animals to humans
It is very likely that we will see emergence of more viral species from animal reservoirs, or more virulent forms of current human viruses or bacteria. The problem is that it is almost impossible to predict which microbe will jump from animals to humans and become more virulent or resist current vaccines or therapies. The only certainty is that other microbes will transmit from animal to humans or evolve to become more transmissible or to evade antimicrobial drugs or vaccines. So, we need to be better-prepared to deal with the next microbe that has the potential to cause an infectious disease pandemic.
We have learned a lot from Covid-19 that will help us plan for the next pandemic. Science and medicine provided the best diagnostic, management and treatment approaches for Covid-19 patients and quickly provided the vaccines that prevented millions of hospitalisations and deaths. The Irish public bought into public health advice, obeyed guidelines and embraced the vaccine programme. While Irish authorities generally handled the pandemic well, some advice seemed to have been made on the basis of political expediency, sometimes ignoring international scientific evidence. It was difficult to understand, for example, the reasons for ignoring the benefits of mask-wearing early in the pandemic, the value of antigen testing, the benefits of good ventilation and the advantages of heterologous vaccination.
So, we need a pandemic-preparedness plan, built on a solid foundation of scientific evidence and research. We need the best clinicians and scientists, including infectious disease experts, immunologists, virologists, epidemiologists, engineers and computational scientists working together in a national research centre focused on pandemic preparedness. This would allow rapid introduction of effective surveillance systems, diagnostic assays and modelling to map the spread of the microbe, and would also contribute to the global research effort in the rapid development of drugs, vaccines and other approaches to control the infection. A critical mass of experts in a research centre focused on pandemic preparedness would position Ireland to effectively interact with leading international groups in cognate areas, allowing us to rapidly exchange information at the highest of levels in order to respond effectively to emerging threats from new infectious diseases.
Kingston Mills is professor of experimental immunology at Trinity College Dublin and Cliona O’Farrelly is professor of comparative immunology at Trinity College Dublin. A public discussion on pandemic preparedness will be held in TCD on Saturday, June 11th.* tcd.ie/COVID-19immunology/conference/
*This article was amended on June 7th, 2022